Mars Opposition

Mars is Unusually Bright and Close to Earth in July and August 2018 A Guide to Observing Mars in Opposition

By Nalayini Davies

Mars Is Close

Elon Musk’s Space X has plans to start colonising Mars by 2024 as it is the planet that is closest and most similar to Earth. He plans to place a million people there in 40 to 100 years!

And Getting Closer - A Rare Event

On 31 July 2018, Mars will be at its closest to us since 2003, which was the closest approach in 60,000 years. This is an opportunity to take a peek at the surface of Mars. With a modest telescope and very little astronomical knowledge you will have the opportunity to see Mars’ white polar caps and volcanic plains. Mars will reach 24.3 arcseconds in size at a distance of 57.6 million km which is 0.8 arcsecond smaller than it was in 2003 when it was at a distance of 55.8 million km on what was its closest approach in 60,000 years, a record that NASA expects to stand until 28 August 2287!

Why is it Worth Observing?

Mars is the only planet whose surface details can be observed from Earth – Mercury is too small and all the others are covered in clouds.And Mars is especially photogenic during opposition because it can be seen fully illuminated by the Sun when viewed from Earth.

An Ideal Event for Beginners

This event is particularly suitable for astronomy beginners as Mars will be prominently and distinctly visible all night and is very easy to locate in the sky.

Although you’ll need a telescope (see our special Mars Dobsonain packages) to observe the features of Mars, the easy to use, portable and cost-effective “Dob” – the Dobsonian design Newtonian telescope - is all that will be required.

The 6-week viewing period of July through August will give observers the opportunity to see the various surface features of Mars as the planet rotates and presents different aspects of its surface. Unlike a single-night celestial event, this event’s 6-week period will offer many observing opportunities, despite some likely inclement weather during the period, and provide the opportunity to practice and improve observing skills through repeated viewing.

11 Mars Facts

Location in the Solar System: 4th planet from the Sun, Earth’s immediate neighbour with its orbit lying just outside that of Earth’s.

The Size of Mars: Diameter of 6, 792 km, and at just over half that of Earth it is the second smallest planet in the solar system.

Average Distance from the Sun: 227.9 million km (Earth is 150 million km from the Sun).

Greatest Angular Size in the Sky: 25.1 Arcseconds (there are 60 arcseconds in an arcminute and 60 arcminutes in a degree and your little finger held at arm’s length covers one degree of sky). On 31 July 2018: 24.3 arcseconds.

Number of Moons: 2, Phobosand Deimos.

What is Opposition

As Mars and Earth orbit the sun, every 26 months, Mars and the Sun are on directly opposite sides of Earth i.e. in opposition.

Because it is closer, Mars is bigger and brighter around the time of opposition.

But every 15 or 17 years, the opposition coincides with a time when Mars is closest to the Sun in its orbit i.e. at perihelion. This year, Mars is at its closest on 31 July, just a few days after it reached opposition on 27 July. This is what makes it such a rare occurrence. At opposition, Mars will appear due North at midnight local time.

The Best Time to Observe Mars

From now through to the end of August, Mars will be at minus 2.5 magnitude in the constellation Capricornus.

On 24 August it briefly moves to the constellation Sagittarius before standing still on 28 August and resuming direct motion after 2 months in retrograde.

The observation at the time of opposition on 27 July will be impacted by the full moon being nearby but this situation will improve a couple of days later.

The hour by hour best times each week as calculated by Auckland’s Stardome Observatory and Planetarium is given below:

Best Hours to View Mars in Opposition (Source: Stardome Observatory and Planetarium)

Where can Mars be Located in the Sky?

Mars will be in the sky all night from now until the end of August – rising in the East and setting in the West. It is easily located as the bright orange-red star-like object which doesn’t twinkle like stars.

Viewing Mars - Observing Options

Naked-Eye to see the distinct orange-red colour of Mars and how it compares to other celestial objects in the sky both in brightness and colour.

Binoculars will only show an orange dot of light with no better viewing than naked-eye, so Mars in not a binocular object.

Telescope of 6” or greater aperture will show the features of Mars.

The 8” Dobsonian telescope is our most popular telescope and ideal for viewing Mars.

Photographic equipment in conjunction with a telescope will enable you to take photos of Mars.

These are all discussed in greater detail below along with links to our YouTube videos.

Naked-Eye Viewing

Mars will be a beautiful naked-eye object throughout July and August, easily seen with a striking orange-red colour in the East. It will also help trace the ecliptic (the apparent path of the sun and the planets in the sky) by first locating Mars and then planets Jupiter and Venus which are the other two brightest objects in the night sky at this time. Slightly less bright Saturn and early setting fainter Mercury i.e. all 5 naked eye planets are all present in the sky and can be traced through the ecliptic found through Mars.

The rusty red colour of Mars is the result of large quantities of iron oxide (i.e. rust) in its surface rocks.

It will be visible in the sky all night and rises higher each night from early-July to mid-August which makes it easier to observe with each passing day i.e. making the viewing in August more convenient.

Telescope Viewing

Mars is the only planet whose surface details can be observed with a telescope from Earth – Mercury is too small and all the others are covered in cloud.

The bigger the aperture the more detail you can see so a 10” reflector telescope shows more than an 8” and an 8” shows more than a 6”. The greater the magnification, the better the viewing so the use of an additional Barlow lens in conjunction the two lenses of the telescope (one is for greater magnification and the other one offers a wider field of view) would enhance the experience.

See Mars’ White Polar Caps and Volcanic Plains

Telescope viewing can reveal Martian features such as white polar caps and volcanic plains. The polar ice is mostly frozen carbon dioxide and the extent of it varies with Martian seasons resulting from its 25-degree axial tilt.

The image of Mars will be upside down through an astronomical telescope so uppermost in view will be the South Pole.

With repeated and committed viewing, Syrtis Major, Mars’ most prominent dark surface marking (a “V” / triangular shape) is also observable. This is a sloping area of darker sub-surface rock that is periodically and temporarily partly covered by paler dust.

The atmospheric pressure on Mars is less than 1% of Earth’s mean sea level pressure. Mars’ atmosphere is also significantly thinner. This leads to even the slightest of breezes on the surface resulting in dusty whirlwinds of surface soils. Such dust storms on Mars can obscure the surface markings but these storms are more common when Mars is closest to the Sun in September.

Replay

As Earth rotates about 40 minutes faster than Mars, over a period of a few weeks it’s possible to see much of Mars’ surface, and this provides more opportunities to see surface features potentially missed during earlier observations.

Changing Views of Mars through Telescope Image credit: NASA

Observing from a dark site under clear moonless skies it is also possible for a committed observer to see the Martian moons, Phobos (+10.5 magnitude) and Deimos (+11.6 magnitude).

Enhancing the Observing Experience – See More

When observing through telescopes, the use of filters can sharpen details.

Barlow Lens

A Barlow lens will help with magnifying the image so you’ll see more detail.

Filters

The use of filters will enhance the viewing and a wide range of colour filters are suitable (e.g. Green or Blue filter will enhance the polar caps and a Red or Orange filter will enhance the darker details like Syrtis Major).

Guides

One “sees” as much as one “knows”, so using an astronomical guide bookwill improve your knowledge and through that enhance the observing experience.

What are the Options for Imaging Mars?

Astro-sketching and Astro-photography

The Astronz introduction to imaging theplanets. Great for Mars, Jupiter and Saturn.

Astrophotography by Auckland Astronomical Society Member Rolf Olsen from Auckland in November 2015 has captured the surface markings

Surface markings and Storm on Mars (Image Credit: Shaun Fletcher)

Let’s Observe!

We are fortunate in New Zealand to have Mars so close to us in our night sky. And it will be there all night from now until the end of August.

Try to take this rare opportunity to closely observe the planet which one day will likely be the second solar system home for humans and our stepping stone to the stars.

Just a few days ago, although Mars is not yet at its closest, Auckland Astronomic Society/Astronz’ Andy Cho sketched an image of what his eyes saw looking through his eyepiece of his 16” Dobsonian telescope from Takapuna around 11.30 pm clearly showing the polar cap and indications of the surface darker regions: